The bits' and bit cones' angular velocities are variable with time. All published papers on cone bit kinematics, however, are based on the supposition that the motions of cones are uniform. This supposition, therefore, has been the main obstacle to determining the objective law of the working cone bit. The apparatus, methods, and tests results for measuring the bit and cone instantaneous angular velocities are described. A new theoretical analysis of cone bit motion is proposed and some interesting new conclusions are obtained that will help designers and users of cone bits.